mazda 6 radio control problem...
 

I just bought a used 2005 mazda 6i 2.3 4 door sedan and the radio control that adjusts the Bass/Treble/Balance/Fader does not work. I can turn that knob to adjust the station, but when you puch it into make a adjustment to the Bass/Treble/Balance/Fader, it will not access that mode. Any advice here would be great...........also the CD player does not work at all.
Help? Is there a good place to by OEM parts online at a good price?